your doors might be loose and not making complete contact with the rubber grommet that gets pushed in..
this was happening on my passenger side door, and my temporary solution (which is still there to this day, almost 3 years later) was to put a piece of double sided tape on the part of the door that pushes the sensor in, and another piece on the button, but I didn't take the plastic off the tape on the outsides, otherwise they'd stick together when I closed the door..
so yeah, you might wanna tighten the bolts on your door...